Besides large coverage and large program capacity, wireless communication broadcasting has a most excellent characteristic of its broadcast capability which can be point-to-point and point-to-face, and it has high transmission bandwidth with low cost. Thus, as an important component of information communication industry, the wireless communication broadcasting plays an important role in the construction of national information infrastructure and realization of normal service and national information security strategy.
With years of research and development, the digital wireless broadcast has obtained many achievements which reaches practical use stage. Presently, there are 4 wireless digital television broadcast standards in the world:
1) Digital Video Broadcasting (DVB) Standards Series.
DVB is proposed by European Telecommunications Standards Institute (ETSI). After the Europe stopped development of Digital-to-Analog mixed television system in 1993, it began to undertake research on digital television broadcast system, and successively issued Digital Video Broadcasting-Satellite (DVB-S), Digital Video Broadcasting-Cable (DVB-C), Digital Video Broadcasting-Terrestrial (DVB-T) standards and Digital Video Broadcasting-Handheld (DVB-H) standard based on DVB-T.
The DVB-S standard in the above mentioned standards utilizes single carrier QPSK modulation, uses cascaded convolution code and RS code as channel encoding, scrambles with Pseudo-Random Bit Sequence (PRBS), uses wireless satellite links, which is only adaptable to fixed receiving system rather than mobile terminal devices. The DVB-T standard uses multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) modulation technology and encoding technology of cascaded convolution code and RS code, which is adapted to open-ground transmission, however, the moving speed is low. Although the DVB-H system optimizes for mobilization and handheld purpose, the optimization is not sufficient due to the limitation of DVB-T coding and modulation technology.
2) American ATSC Standard
The American ATSC standard is a single-carrier digital television terrestrial transmission standard proposed by Advanced Television System committee (ATSC), which can support fixed receiving of digital television with standard definition and high-definition. However, the performance thereof is inferior under mobile reception condition and can not support satellite transmission.
3) Japanese ISDB-T Standard
ISDB-T is an Integrated Service Digital Broadcasting-Terrestrial standard revised by Japan digital broadcasting expert group which achieves terrestrial broadcasting of various digital services with OFDM technology, convolution code and RS code. However, the performance thereof is inferior under mobile reception condition and can not support satellite transmission.
4) Japan-Korean Digital Satellite Broadcasting Standard
In May, 1998, Toshiba Corp., SKTelecomm Corp., Sharp Corp., Toyota Motor Corp. etc. jointly invested and founded a Mobile Broadcasting Corporation. And it launched a broadcasting satellite in March, 2004, and now it is running into business, providing services for Japan and Korea. The system also uses PRBS, interleaving concatenated encoding, and it transmits in a manner of CDM frequency spreading. Although the Japan-Korean digital satellite broadcasting standard can support mobile reception, the performance thereof is not sound enough, which needs further improvement.